Hyper Suprime-Cam survey maps dark matter in the universe

September 25, 2018

Today, an international group of researchers, including Carnegie Mellon University's Rachel Mandelbaum, released the deepest wide field map of the three-dimensional distribution of matter in the universe ever made and increased the precision of constraints for dark energy with the Hyper Suprime-Cam survey (HSC).

The present-day universe is a pretty lumpy place. As the universe has expanded over the last 14 billion years or so, galaxies and dark matter have been increasingly drawn together by gravity, creating a clumpy landscape with large aggregates of matter separated by voids where there is little or no matter.

The gravity that pulls matter together also impacts how we observe astronomical objects. As light travels from distant galaxies towards Earth, the gravitational pull of the other matter in its path, including dark matter, bends the light. As a result, the images of galaxies that telescopes see are slightly distorted, a phenomenon called weak gravitation lensing. Within those distortions is a great amount of information that researchers can mine to better understand the distribution of matter in the universe, and it provides clues to the nature of dark energy.

The HSC map, created from data gathered by Japan's Subaru telescope located in Hawaii, allowed researchers to measure the gravitational distortion in images of about 10 million galaxies.

The Subaru telescope allowed them to see the galaxies further back in time than in other similar surveys. For example, the Dark Energy Survey analyzes a much larger area of the sky at a similar level of precision as HSC, but only surveys the nearby universe. HSC takes a narrower, but deeper view, which allowed researchers to see fainter galaxies and make a sharper map of dark matter distribution.

The research team compared their map with the fluctuations predicted by the European Space Agency Planck satellite's observations of the cosmic microwave background radiation -- radiation from the earliest days of the universe. The HSC measurements were slightly lower than, but still statistically consistent with Planck's. The fact that HSC and other weak lensing surveys all find slightly lower results than Planck raises the tantalizing question of whether dark energy truly behaves like Einstein's cosmological constant.

"Our map gives us a better picture of how much dark energy there is and tells us a little more about its properties and how it's making the expansion of the universe accelerate," Mandelbaum said. "The HSC is a great complement to other surveys. Combining data across projects will be a powerful tool as we try uncover more and more about the nature of dark matter and dark energy."

Measuring the distortions caused by weak gravitational lensing isn't easy. The effect is quite small and distortions in galaxy shapes can also be caused by the atmosphere, the telescope and the detector. To get precise, accurate results, researchers need to know that they are only measuring effects from weak lensing.

Mandelbaum, associate professor of physics and member of the McWilliams Center for Cosmology at Carnegie Mellon, is an expert at controlling for these outside distortions. She and her team created a detailed image simulation of the HSC survey data based on images from the Hubble Space Telescope. From these simulations, they were able to apply corrections to the galaxy shapes to remove the shape distortions caused by effects other than lensing.

These results come from the HSC survey's first year of data. In all, the HSC survey will collect five years of data that will yield even more information about the behavior of dark energy and work towards other goals such as studying the evolution of galaxies and massive clusters of galaxies across cosmic time, measuring time-varying objects like supernovae, and even studying our own Milky Way galaxy.
-end-
In addition to Mandelbaum, lead authors of the study are Chiaki Hikage, Masamune Oguri and Masahiro Takada of the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) and University of Tokyo; Takashi Hamana of the National Astronomical Observatory of Japan; and Surhud More of Kavli IPMU and the Inter-University Center for Astronomy and Astrophysics.

The research will be uploaded to the preprint server https://arxiv.org and will be submitted to the Publication of the Astronomical Society of Japan.

Carnegie Mellon University

Related Dark Matter Articles from Brightsurf:

Dark matter from the depths of the universe
Cataclysmic astrophysical events such as black hole mergers could release energy in unexpected forms.

Seeing dark matter in a new light
A small team of astronomers have found a new way to 'see' the elusive dark matter haloes that surround galaxies, with a new technique 10 times more precise than the previous-best method.

Holding up a mirror to a dark matter discrepancy
The universe's funhouse mirrors are revealing a difference between how dark matter behaves in theory and how it appears to act in reality.

Zooming in on dark matter
Cosmologists have zoomed in on the smallest clumps of dark matter in a virtual universe - which could help us to find the real thing in space.

Looking for dark matter with the universe's coldest material
A study in PRL reports on how researchers at ICFO have built a spinor BEC comagnetometer, an instrument for studying the axion, a hypothetical particle that may explain the mystery of dark matter.

Looking for dark matter
Dark matter is thought to exist as 'clumps' of tiny particles that pass through the earth, temporarily perturbing some fundamental constants.

New technique looks for dark matter traces in dark places
A new study by scientists at Lawrence Berkeley National Laboratory, UC Berkeley, and the University of Michigan -- published today in the journal Science - concludes that a possible dark matter-related explanation for a mysterious light signature in space is largely ruled out.

Researchers look for dark matter close to home
Eighty-five percent of the universe is composed of dark matter, but we don't know what, exactly, it is.

Galaxy formation simulated without dark matter
For the first time, researchers from the universities of Bonn and Strasbourg have simulated the formation of galaxies in a universe without dark matter.

Taking the temperature of dark matter
Warm, cold, just right? Physicists at UC Davis are using gravitational lensing to take the temperature of dark matter, the mysterious substance that makes up about a quarter of our universe.

Read More: Dark Matter News and Dark Matter Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.